A standard single-control mixing valve such as described in commonly owned U.S. Pat. No. 4,540,023 has a fixed valve plate formed with a pair of inlet ports respectively connected to hot- and cold-water inlet lines and, offset therefrom, an outlet port connected to an outlet line normally leading to a faucet. A movable valve plate sitting atop this fixed valve plate has a mixing cavity open toward the fixed plate and movable to variously overlap the ports. When the movable plate is pivoted about a normally upright axis perpendicular to the interface between the plates it can align more of one of the inlet ports with the mixing cavity and less of the other inlet port to vary the ratio of hot and cold water fed to the outlet port, and when slid in a front-to-back direction parallel to the plate interface it can control the overall extent of overlap to vary the overall flow from the inlet ports through the mixing cavity to the outlet port.
Typically the movable valve plate is pivoted on the bottom end of a lever that is centrally pivoted on a housing liner that is coupled to the movable plate to rotate it about the upright axis. The upper end of the lever is fitted to a handle that is raised and lowered to control volume rate of flow and that is pivoted from side to side to control outlet temperature. Thus the user controls output temperature by pivoting the handle connected to the movable plate about the axis perpendicular to the plates and output volume by rocking the handle, typically in a vertical plane, about another axis perpendicular to the plate axis.
U.S. Pat. No. 4,153,077 describes an alternate system where the lever is pivoted from side to side to control volume rate of flow and is tipped back and forth to control outlet temperature. This alternate system is preferred by some users in that it more closely mimics an older variety of faucet which is rotated to control volume.